"Some years ago a poor man was seen on the quay of the
Louvre, who showed to the amazed spectators the facade of the Institute
through an enormous paving stone. This magic glass which enabled people
to see through opaque bodies, was composed of a tube broken in the middle,
in which was placed a stone; but the two pieces were really united by tubes
(in the supports) twice bent at a right angle, and containing four plane
mirrors inclined at 45°." From Amédée Guillemen, The
Forces of Nature (MacMillan, London, 1877), pg 257.

The Periscope, sometimes called the Polemoscope, was used
during sieges to see over the parapets of trenches. The apparatus at the
left, below, is in the collection of the University of Mississippi, and
was made by James Millington (1779-1868) who was the first Professor of
Natural Philosophy at the University from 1848 to 1853. At the right is
an example at Yale University that was made by Leybold's Nachfolger of
Cologne, imported by James G. Biddle of Philadelphia, and listed in the
1921 Leybold catalogue at $5.00.